(1) Field of the Invention
The present invention is related generally to disposable smoke masks of the type that are fittable over a person's head, and more particularly to a smoke mask of this type with a replaceable filter cartridge to allow for extended usage.
(2) Description of the Prior Art
The prior art describes various smoke masks for use by individuals who need to escape from a burning building or other smoke-filled environment. Generally, these masks are comprised of a hood that encloses the user's head, a visor in the hood to be positioned before the user's eyes, and a filter normally positioned in front of the user's mouth. A separate exhaust port may also be positioned in the hood for expiration.
In order to by effective and commercially feasible, the mask must be economical to produce and disposable. In addition, the mask must be easily donned by an inexperienced user under highly stressful conditions, while still being designed to exclude smoke or other contaminants from inhalation.
Many prior art disposable gas masks have a rubber-type main body that must be stretched when pulled over the user's head. The mask is designed to cling about the person's head to prevent contaminated air from passing by the gas mask and exposing the wearer to the contaminated air. Prior art filters typically include an outer particulate layer to remove particulate matter from the contaminated air, and an inner carbon-activated layer to absorb gaseous contaminants. Generally, the carbon-activated layer is formed of a carbon-saturated material that is effective for only a relatively short time.
U.S. Pat. No. 5,452,712 to the present inventor, incorporated herein in its entirety, describes a smoke mask that provided several improvements over these prior art masks. The mask described in that patent (referred to herein as the '712 mask) is comprised of a hood that fits loosely over the wearer's head, instead of being tightly stretched over the head. A transparent visor, a filter cartridge, and an exhaust valve are positioned in the front portion of the hood.
The mask is secured to the user's head and face in a manner excluding smoke and other contaminants by an elastic strap that is secured at its ends to opposite sides of the mask. Normally, the strap extends across the area of the mask overlying the forehead of the wearer. When used, the strap is pulled downwardly and under the chin, forming a seal extending along opposite sides of the front portion of the mask and under the chin of the wearer.
The '712 mask may also include a second strap that is attached at one end to one side of the bottom portion of the hood. The second strap wraps around behind the neck of the subject, around the opposite side of the neck, underneath the chin, and then extends back up the opposite side of the hood where the other end of the second strap attaches to the smoke mask structure, e.g., with a hook-and-loop fastener.
The filter used in the '712 mask can be of a three-layer or four-layer construction. The three-layer filter includes a particulate filter layer to remove particulates; an activated carbon layer to absorb harmful gases; and a carbon monoxide catalyst layer to convert carbon monoxide to carbon dioxide. The activated carbon layer is preferably formed of a solid bed of carbon for extended usage. The four-layer filter also includes a desiccant filter layer to remove moisture and thereby increase the effectiveness of the activated carbon and/or carbon monoxide catalyst layers.
The layers of filter material may be enclosed within a housing to form a multi-stage filter cartridge. In the preferred embodiment of the '712 mask the multi-stage filter cartridge includes a first generally rectangular or square section and an integrally formed, generally cylindrical rear section having a smaller cross-sectional area. Contaminated air or smoke enters the first section, where it passes through particulate and dessicant filter layers, and then through the rear section that includes the activated carbon filter layers, and optionally the carbon monoxide catalyst filter layer.
The filter pack is secured to the hood by encapsulating the front section of the housing in a plastic covering and fusing the covering to the hood. A circular seal is also used to permanently seal the covering around the front portion of the cylindrical rear section at its juncture with the front section.
While the '712 mask provides several advantages over prior art smoke masks, further advances are still needed. In particular, there is a need for a smoke mask that permits extended usage while still meeting the requirements of economy and disposability. In addition, there is a need for a mask design that is more easily donned under stressful conditions. There is also a need for a mask design that further reduces the stress to the wearer during use. These and other needs are addressed by the smoke mask of the present invention.